I'm uncertain of the definition of the universe but I would assume that it includes empty space as well as the celestial bodies that are in it. If one were to travel through space for an infinite amount of time would it be possible to come to the end of the Universe? If it were possible what would there be at the end? Nothing? Empty space? Is empty space not 'something'? How about a brick wall. What is on the other side of said wall? In my own personal opinion infinity is......... period. Space and therefore the universe must be infinite.

 

If this thinking is flawed please explain. Thank you.

Your model assumes that the unverse on a large scale is absolutely flat. However if it is at all curved, then you could travel and eventually come back to where you started,

Your model assumes that the unverse on a large scale is absolutely flat. However if it is at all curved, then you could travel and eventually come back to where you started,

 

Negative curvature might allow the universe to be infinite - whereas positive curvature might allow you to return where you started